A Chico fraternity pledge died of water poisoning, authorities said Thursday as experts warned that the dangerous hazing ritual has killed at least one other person as fraternities are replacing alcohol bingeing with excessive water-drinking.

Matthew Carrington, 21, of Pleasant Hill had a heart attack and died during "Hell Week," authorities said, as he was in the final stage of a monthslong process to rush Chi Tau fraternity -- a rowdy house that had been expelled from California State University Chico in 2002 for repeated violence and alcohol violations.

Water bingeing is becoming an increasingly common hazing ritual, especially inside rogue frat houses such as Chi Tau, said Hank Nuwer of Indiana, a national expert on hazing and author of four books on the topic.

"These unsanctioned fraternities have no standing with the university, so to build prestige they like to come up with the most grueling initiations," Nuwer said, "And they think water is safer than alcohol, but it can also be deadly."

Forced water consumption and heavy exercise are known to dilute the salt content of blood to the point where it interferes with brain, heart and muscle function. Without enough sodium, the brain swells and victims can suffer fatal comas.

Carrington's friend who survived the hazing told police that he and Carrington each were forced to drink about five gallons of water. They were kept up all night in the fraternity's basement doing rigorous calisthenics as fraternity members splashed them with ice water and turned fans in their direction.

The Butte County coroner's report listed hypothermia as a significant contributing factor to Carrington's death.

"As universities crack down on hazing, frats are turning to other things like water and milk to haze pledges, kind of like an 'in your face' thing to the university," Nuwer said.

Another water-hazing death happened in a similar unsanctioned fraternity with aging alumni, Nuwer said.

In March 2003, State University of New York freshman Walter Dean Jennings III was pledging a renegade fraternity that had also been expelled over drinking violations. He was forced to drink so many pitchers of water through a funnel that the sodium in his body dropped to lethal levels and his brain swelled. The autopsy confirmed he died of hyponatremia.

That same year in Texas, a young pledge at Southern Methodist University went into a coma after being forced to drink too much water in November 2003. Even after he passed out, fraternity members propped him up and made him drink more. He suffered hyponatremia and pulmonary edema -- water in the lungs. He was hospitalized for a week and fully recovered.

Participants in both incidents faced criminal charges and sanctions from the college.

In Chico, a message from former Chi Tau President Jesse Chrisp was posted on the fraternity's Web site informing alumni members of Carrington's death.

"There was no alcohol involved," he wrote. "Those of us older guys still here suspect that hazing by water consumption was the cause." Chrisp added in the letter that he's no longer involved with Chi Tau.

University officials are working with police to try to figure out how many of the Chi Tau members involved in the incident are students, outsiders, or alumni who have come back to live the frat lifestyle.

Nuwer said hazing can happen in both sanctioned and rogue fraternities. "Freelance" fraternities are not uncommon in university settings, he said, but they can be more dangerous for students because they operate with impunity outside university supervision and often house aging alumni eager to relive the "Animal House" lifestyle.

"A really big suggestion for universities is to strip alumni status from the fraternities they toss off campus, so alums aren't allowed to come back and move in," Nuwer said.

Leo Boyle, a Boston trial lawyer who was the first to get a fraternity indicted for manslaughter in a 1997 alcohol-related hazing death at Massachusetts Institute of Technology, said cases like his and the one in Chico are reasons the public no longer tolerates hazing as a rite of college passage..

A candlelight vigil for Carrington will be held today outside Chi Tau fraternity, at the corner of Fourth and Chestnut streets in Chico. The funeral will be at 1 p.m. Wednesday at New Life Church in Alamo, 2501 Danville Blvd.